Shear and tension patch



July 13, '1948. J. KlNrAs Y sHEAR AND TENSION PATCH Filed Dec. 2,- 1945 ooooooooooooooooooooooeo INVENTOR. l L//A/ /f//vr/Qs OETTP/VE'V Patented July 13, {'1948 g UNITED STATES i l sama igoyrarc John Kintas, Wichita, Kaaassigni-ftc Beech Aircraft Corporation, Wichita, Ranst, aicfurporation of Delaware jApplieatidnfDec-ember 2, isiai'serilm9512353 V".'hejin'vent'ion here disclosed relatesto the testing lof thin panels, such as largely employed vin the 'construction of aircraft.'

Forlstrength testing and other purposesitis Under such test conditionsfurthermore, it is necessary that the strength of the panel be not -altered by the stiffness of the load appl-ying means 'and that the applied load be substantially uniformly distributed over an 'area ofV sufficient size tofpreclude failures of a localized nature.

- YThe main objects of this invention are -t'o'provide-satisfactory means for applying load to any vflat or curved surface in directions normaL'paraI- 1e1 or skewed reattive to suchsurface, 'without deforming or altering stiffness orr other characteristics and which will be readily applicable to the-'panel or otherfsur'face under test.

Other desirable objects and the novel features 'bywhich the purposes of the invention are attained are set forth or will appear in the course of the following specification:

The drawing accompanying `and forming' part "of the Aspecification illustrates certain present 'typical embodiments of the invention. Structure Ihowever, may be modified and changed vas re'- igards such illustration, al1 within the true intent and broad scope ofthe invention as hereinafter defined and claimed.

Fig. 1 in the drawing-is abroken and partsectional view, illustrating a shear patchfapplied 'to v'an aircraft wing panel.'

12 is avbroken plan view of the same. Fig. 3v is a side elevation of a tension patch 'applied to the back of a plastic pilot seat.

impervious more or less hard surfaced material,

such as aluminum, plywood or the' like.

While any suitable flexible material of any shape or size may be employedthe patch is shown as comprising a pad or stri'p'yof cloth, elongated in the,V direction of pull, conformed to and secured continuously an'duniformly to the surface of the panel by an underlying layer f adhesive 9.

Traction is applied in the illustration by a pull bar l0, located in the bight Il, of the material s claims. (o1. '13-isc) foii'ife bakan'dlscred to the patch @portion by 'stitching-'ill "The piiilbarlis loa'ded'by weights 'i 3,connectejd 1by cable l 4, f-passingver the "pulley il5,`to` the pull bal'.

'The tension lpatch differs" frm'the shear patch, particjilarlyin the netho'dlof applying the load.

As -shown in Figs. 3, 4 and 5, thetnsion-patch vis made up of a layer ofwo'ven fabric 8a, secu-red 'tothe specimenundertest, in thiscase, the back Ypanel la, -of a `plastic pilot seat, by a continuous "layer fv'aldhsive 9a, but Ilill of the loading cable 14a, is 'applied through a conically distended fabric pull disc I6, secured'abot its edges to the patch disc by heavy stitching |11.

Connection 'of V'the "cf'ible t the pull disc is effeetedfty a 'metal ban rs, swaged on tn'eeqpf the 'callefajd sate'dna conical or dimpled nietal Waslmrv 9, erigagedwlthin the pun disc. Y

t'wo 'of fittings illustrated have been ""'ind Ito answer 'for Ii'lst testing purposes. The -sig'l'e layer of strong flexible fabric, ysuch as heavy canvas, readily conforms to the 'surface 'ndertstand can be rinlyattached to the test surface by 'a cement will adhere yto a fm'etallie or other relatively yhard surface an'dpenetrate the woven fabric and inrhardening or solidifyg, for'n fa positive, practically permanent b. btwe'n the two. This V-uicm of the patch Withtle fest :piece is acolplish'd Witlicfu't altelfing or iimpairing the surface or body `characteristis ofthe -'1"natrial'der`t'st. ]En`l th first in'- rrstance, Figs. 1- and 2, the s'h'eanlojd'isapplied to the alinirim skin on"tlie"nose of ari-airframe, `uniforinly, over a siiiiiciitly' 'ete'ride'd areaffo'r 'test 'ptir/poses, "withiit {indent-Jing, yrSent'rati'ng' lor Iiii V any other way altering4 the physical character fof the structure. Here 'the load is applied imiformly in the'genje'ral direction of extent of the patch.- Similarly inthe tension patch Figs; 3, 4 and "5, *the structre is not loaded' tnrpugh the vrfifziln. The fittings transmit load, uin the second instancajtnrou'gh the' fabric pun disc, 't0-'the cemented dise andthe loaded :surface-isi ritdeformed inf lany (tirait vsin'ce the Alarger clotli disc, onlyjisjRiemer'1te`d'tothestructure.b .y Y

while 'diffrent adhsives which will meet Ythe requirements of the invention may' be employed ariddifferet modes of appli-cation Used, they following-l is citedfas one preferred example.

Y First the 'Surface to the-* patch, t9 be applied `sntn'd' `be thoroughly cleaned'. Then assuming this to be an aluminum surface, two prime coats of 62730-3 are brushed on, each coat being permitted to become thoroughly dry, 30

viously ap lied two coats on the canvas and dried' to a tack ondition. The canvas, with this total of four brush coats is then applied over the two coats on the Wing section and rolled or wiped,v

down into continuous, firm engagement. The bond may be air dried for about 12 hours and 4 aircraft structures comprising a load applying layer of thin, nat, flexible, non-stretching, strong interwoven fabric sufficiently pliable to be conformable to the varying surface contours of aircraft structure, said pad having incorporated therein, in its flexible, conformable state, an adhesive which can be treated to bond the pad to the surface of a part to" be tested and whereby said pad may be applied directly to the surface by simply pressing the same into smoothly conformed engagement over the surface and treating the adhesive in the pad to bond the pad in its conformed state to such surface, and a load api l plyingpulllconnection flexibly connected with a then heated under infra-red lamps forabout .31 hours. After removing the lamps, the entire unit"v should be permitted to cool before testing shear strength.

A The patches may be of various sizes and shapes to meet the needs of particular tests and 1twoor more may be used, instead of a vsingle patch. These patches may be applied in restricted4 or more oir less inaccessible places. The conforming of the flexible patch material t0v the surface with interposed adhesive and baking in that relation by infra red rays, provides a bond which will uniformly distribute and carrythe full test load and without having alter-ed the natural characteristics of the test piece. The test-loads as `has been seen, may be applied at any angle orin line or parallel with the absolute or approximate plane of the surface under test. Y

What is claimed is: c j

1. A loadingpatch for the shear testing of aircraft panels, comprising a, load applying l-ayer of thin, flat, flexible, non-stretching, strong interwoven fabric` conformable by'reason of its ilexibility to the varying surface ccntoursof 'aircraft panels or the like, adhesive `capable Gif-,bonding with the surface of such panels, said adhesive incorporated in and impregnating saidpermeable Woven fabric in its exibly conformed condition and forming at the surface of the'fabjric which is opposed an-d conformed to the surface ofithe panel a continuous, coextensive, tenacious bonding layer,` saidwoven fabric having an extended unattaohedV portionat one edge folded backupon itself and secured inthe form of a .big-ht, apull bar seated in said bight and means `connected with said pull bar for applying a test load thereto'.

2. A tension loading patch for tension loading an aircraft panel or other object comprising a load applying` layer of thin, flat, flexible, nonstretching, strong interwoven fabric conformable by reason of its flexibility to the varying surface contours of aircraft panels or other objects tozbe tested, adhesive capable of bonding with the surface of the object to be. tested, said adhesive incorporated in andimpregnating said permeable Woven fabric in its flexible vconformedcondition and forming `a continuous coextensive'tenacious bonding layer'at that surface ofv the fabric which is opposed and conformed to the surface of the object under test, a fabric pull vpad securedabout its rim and over la considerable portion of its area to saidflexible conforming fabric andia pull connection attached to the central portion of said fabric pull pad and inside that area which is attached to the flexible conforming layer Vof fabric.

3. A loading patch for the strength testing of considerablearea of said pad and thereby arranged tdtransmit the test load substantially uniformly tothe pad and thus to distribute the load substantially uniformly over the surface to which the pad is attached irrespective of variations in contour of the surface.

4. As anew article of manufacture, a loading patch for strength testing aircraft structures comprising a. substantially circular load applying pad of strong, flexible, heavy canvas, a'conically` distended'smaller pad of heavy canvas secured over the outer face of said first pad by heavy stitching about the rim of the same, flexible adhesive medium incorporated in said load applying pad and extending in a bonding layer over the inner face of the same, said flexible bonding layer being conformable along with said flexible canvas load applying pad to varying surface curvature of aircraft structures and said adhesive being of a character which can be treated to form a bond with the surface `of a structure under test and wherebythe patch may be united with various surface conformations bytreating saidadhesive 4to, effect bonding with said surface and pressing said pad into smoothlyv conformedengagement with the surface, a centrallyV disposed load applyingv washer within said conicallyY distended` pad and a pull connection engaged with said washer.

5.v As a new article ofl manufacture, `a loading patch for strength :testing aircraft structurescomprising a layer of strong,l flexible, heavycanvas and a layer of heavy canvas secured by fheavy stitching over the outer face of said. first layer, flexible adhesive incorporatedin saidflrst layer and extending over the inner face 0f thesame as a substantially continuous bonding layer, said `adhesive being of a nature which can be treated to effect bonding of the surface layer withthe surface of the structure to be testeddand whereby said loading patch may be united vvvithvstructures o-f varying curvature by simply treatingthe-ad- Vhesive to effect bonding with the s'ufacefofv the 

